1. Field of the Invention
The present invention relates to a high speed method and device for applying labels.
2. Description of the Related Art
An application of relatively small labels to relatively large, flexible bodies, such as cartons and newspapers, has been an expensive, time-consuming and an inaccurate activity. The flexible bodies, such as cartons and newspapers, have been difficult to adhere adhesive articles and align with a labeling device. Furthermore, it has heretofore not been possible to adapt a device for labeling bottles to a device for labeling cartons and newspapers because the cartons and newspapers often travel at a very different rate than other types of products. Typically, the higher rates are much faster than can be accommodated by a conventional labeling device. The result is improper registration between the carton and the label. The poor registration becomes catastrophic within a very short period of time in a rapid labeling operation. A consequence is the significant loss of production time and maintenance that is required to correct and, repair damaged equipment in the label process. Excessive raw label material must be destroyed. Mislabeled products may also have to be destroyed.
Furthermore, it has always been difficult to increase the rate at which labels are applied to any type of article, while maintaining a sufficient level of consistency and avoiding damaging the articles, the labels, or the supply web.
The Eder patent, U.S. Pat. No. 5,464,495, issuing Nov. 7, 1995, describes a method and an apparatus for applying labels to containers and the resulting containers. With this method, containers are transported on rotatable support plates which are arranged in a circle on a rotating turntable. A leading edge of a label is adhered to a container as the container orbits past a vacuum-type label transfer drum. A curved guide which is tangential to the cylindrical body of the container, as the orbiting and rotating container passes, causes the label to wrap completely around the container. One of a circular array of heat-sealing elements which are rotated with the turntable adjacent each support plate is cammed radially outwardly of the turntable into contact with the region on the container where the trailing end overlaps the leading end of the label. This action fuses the ends of the labels together. The cam profile is adjustable in length to keep the time during which the heat-sealing member is in contact with the label ends overlap constant and independent of the rotational speed of the turntable.
A device for the precise delivery of labels includes a mechanism for web manipulation, a mechanism for label positioning, and a mechanism for micro-adjustment of the device for the precise delivery of labels. The label positioning device interacts with an article, such as a carton 15 or newspaper, in order to transfer labels from a web to the article.
The present invention also includes a method for applying labels to articles so that the labels have a consistent and precise alignment. The method includes providing a device with a web manipulation mechanism, a label positioning mechanism and a position mechanism micro-adjuster. A peel tip component of the device is spatially adjusted in a precise manner in order to produce precise alignment between the labels and the articles to which they are applied, at a variety of manufacturing speeds.
The present invention also provides a positionally based system for matching the placement of a label with the arrival of an article at a nip point, wherein the label is applied to the article at the nip point. In the most preferred form, the web carrying the labels is moved continuously and this movement is accurately adjusted for each article that passes through the nip point. To accomplish this a pitch sensor is provided that detects the pitch between the articles as they are moved along a conveyor. Subsequently, the articles location is detected by a registration sensor. This detection occurs at the approximate time that the preceding object receives a label. In addition, a label sensor is located near the supply web (prior to the nip point) to determine the pitch of the labels. The same sensor is also used to determine the position of a leading edge of each label.
A system controller receives all of the data and controls the distribution of the labels, by controlling the motion of the supply web. When the pitch of the objects is measured by the pitch sensor, this data is transferred to the system controller and an xe2x80x9celectronic gear ratioxe2x80x9d is defined for that article. That is, in order for a label located at a distance from the nip point, and an article that is similarly located some distance from the nip point to arrive at the nip point at the same time, some ratio of movement between the article and the label must be defined. For example, if the article is exactly twice as far from the nip point as the label, the article will have to move two incremental units for every incremental unit that the label moves. As such, the system is entirely positionally oriented and therefore fully functional, independent of velocity. Once this ratio is determined, a closed loop servo driving the supply web corrects the position of the web to achieve the desired ratio (since movement of the article conveyor is relatively constant).
When the article is detected by the registration sensor, the ratio that had been determined for the particular article is then implemented. Theoretically, the label and the object should then arrive at the nip point at the same time. This assumes perfect movement of the supply web and perfect spacing between the labels. Since neither occurs with sufficient reliability, a final adjustment is made. That is, when the article is detected by the registration sensor, the label sensor looks for the leading edge of the label to be placed. Since there is a difference in the distance between the registration sensor to the nip point and the distance between label sensor and the nip point, the label will be sensed at some point after the article is detected. This interval is predefined and any deviation noted (i.e., the label being detected earlier or later by the sensor) is recorded as an error. The system controller then causes the servo motor driving the supply web to temporarily accelerate or decelerate (with respect to the rate of motion of the product conveyor) to account for this error. Once the error is corrected, the supply web resumes moving at the predetermined ratio. This secondary adjustment occurs very rapidly and is generally very small. However, this adjustment is separate and distinct from the initial setting of the electronic gear ratio.
In operation, the supply web supporting the labels will move continuously. Adjustments will be made to the motion of the supply web; however, it will normally not stop moving unless an article is missing from the conveyor. The label and the article will arrive at the nip point at the same time. The supply web is pulled around the peel tip, thus causing the label to separate from the web. The continued motion of the web causes the label to move forward toward the nip point. The peel tip is positionally adjusted so that as the label enters the nip point, only a very small portion of the label remains adhered to the supply web. Entry into the nip point and partial attachment to the article causes the label to be pulled from the supply web as the article travels much faster than the supply web. Since only a very small portion of the label was in contact with the supply web, this pulling action has no negative impact on the supply web itself. Subsequently, a roller (forming the nip point) applies the remainder of the label to the object. Alternatively, the label could be launched or shot into the nip point. That is, no portion of the label will remain adhered to the supply web when the label enters the nip point. Such an arrangement requires very precise alignment, a high tolerance in the manufacture of the labels, and accurate control of the supply web.
The continuous motion of the supply web allows labels to be placed on articles at a far higher rate than other types of label applicators. Previous label applicators limited the speed at which the articles could be conveyed. That is, it has always been possible to increase the speed of the article conveyor, there just has not been a practical way to consistently apply labels at these increased speeds. The simplest traditional approach is to have the labels (supply web) travel at the same speed as the products (known as the wipe-on method). This has proven to be undesirable at higher speeds because the supply web cannot be economically manufactured to withstand the forces imparted at such high speeds. Because of the electronic gearing of the present invention, the supply web can move continuously at a lower rate yet still effectively match a higher rate article conveyor. As such, errors or defects on the labels or on the supply web are less problematic. For example, if a minor tear occurs in a supply web, the previous applicators would likely cause that tear to enlarge and likely sever the supply web due to the high forces involved (wipe-on method), the sheer forces generated during the frequent starting and stopping, and/or the tugging occurring with previous peel tip applicators. In the present system, such defects can be ignored because the supply web is moving constantly and consistently. Ultimately, this will reduce the number of failures caused by misalignment or catastrophic system shutdowns, thereby increasing efficiency and reducing cost. The present invention is also advantageously positionally based; that is, it will function properly regardless of the speeds being utilized.
In another embodiment of the present invention, a single registration sensor is utilized to detect the position of an article to be labeled. In operation, the supply web is advanced so that a large percentage of a label is separated from the supply web. As such, the label extends from the supply web (at or very near the peel tip) towards the nip point. The rigidity of the label is relied on to maintain this orientation. The position of the peel tip is very accurately adjusted so as to accommodate the length of the label in this manner. Just as the article approaches the nip point, the supply web advances, causing the label to enter the nip point. As explained above, once a portion of the label is adhered to the faster moving object, the label is pulled off the supply web. Since the contact (adhesion) between the label and the supply web is minimal, this pulling of the label has no negative effect on the supply web. Once done, the supply web again advances and stops, leaving the next label poised to be applied. The accurate deployment of the label to the nip point allows for labels to be applied to objects traveling at a high rate of speed without requiring the intermittent speed of the supply web to match or even approach the speed of the objects being conveyed. The registration sensor is used to detect the presence of the article as it approaches the nip point, and hence trigger the forward movement of the supply web.
In yet another embodiment, a single sensor is used to determine the pitch of the products as well as serving as the product registration sensor. The single sensor is placed upstream from the nip point and relies on the predetermined distance between the sensor and the nip point to effectuate the electronic gear ratio. This embodiment functions similar to the first except that the electronic gear ratio will be implemented a certain number of encoder pulse counts after the product passes the single sensor, rather than utilizing a second or registration sensor. This system benefits from the continuous motion of the supply web, however, it has fewer components involved. Its accuracy is dependent upon the tolerances of the encoders used and the methods employed to record and monitor pulse counts. That is, if the detection of encoder pulse counts used to engage an electronic gear ratio is embedded in a software subroutine, the practical limits of computing/microprocessors could reduce the accuracy at very high production speeds. However, a separate controller/detector could be utilized to monitor encoder pulses with respect to the single sensor, thus reducing or eliminating this problem. Obviously, microprocessors are available to perform this task at the speeds required, however, price considerations are also a factor.
As mentioned above (and equally applicable to all embodiments using a peel tip), the label will essentially have to span the gap between the peel tip and the nip point. Often, the labels used will have sufficient rigidity to accomplish this. However, some types of labels may simply be too flexible. As such, a further aspect of the present invention is the use of various label supporters. Rods may be placed from the peel tip to the nip point (above the label), to guide the label and to prevent it from moving upward. In addition, an air jet can be positioned to direct a stream of air towards the underside of the label, thus causing it to closely follow the rods. Similarly, a plate extending from the peel tip to the nip point can be utilized with or without the air jet. Alternatively, the plate could incorporate a vacuum which pulls the label towards the plate, allowing the plate to effectively guide the label to the nip point. Either the plate or the rods can be configured to extend just to the nip point, or, if the nip point utilizes a roller, slots can be cut into that roller. This allows the rods or the plate to extend past the outer circumference of the roller (which effectively applies the label to the object), thus leaving no gap at all for the label to span unsupported.